The present invention relates to an arrangement for the relative adjustment of the rotation angle of a control shaft with respect to a driving wheel, particularly for an internal combustion engine.
DE-C 42 33 250 suggests, for prevention of noise generated in the drive of a known arrangement, that, among others, a prestressed diaphragm spring be arranged between the parts which can be angularly moved relative to one another. With the selection of an operating range for the provided spring path in a positive course of the characteristic curve, a diaphragm spring will result in considerable changes in the prestressing forces toward lower values even in the case of slight changes between the components in the spring path direction. These changes also reduces the extent of the frictional damping between the angularly movable parts.
Diaphragm springs with positive and negative courses in their characteristic curves are, of course, well known as shown in Haeders Hilfsbucher Fur Maschinenbau, Konstruieren und Rechnen Fur Studium Und Praxis, p. 316 (FIG. 3) and Niemann, Maschinenelemente, p. 192 (FIGS. 12/16) (1954). These characteristics depend on value obtainef for calculations off a spring configuration, particularly of the height of the cone of the diaphragm spring.
It is an object of the present invention to provide an improved arrangement of the above-mentioned type by way of which a reduction of the frictional damping between angularly movable parts connected with operationally caused changes of the components is securely avoided.
The foregoing object has been achieved in that the diaphragm spring is selected to have a course of a characteristic curve which is relatively negative in sections and is arranged in a prestressed manner such that, along a predetermined operating range, a spring path in the relatively negative course of the characteristic curve is assigned to the diaphragm spring.
It is an advantage of the present invention that, in an operating range of the diaphragm spring which is averaged at the reversal point of an essentially uniformly curved, relatively negative course of the characteristic curve, with axial deviations of the measurements of the components caused by the operation, the spring tension will increase and a reduction of the frictional damping will therefore not occur.
For advantageously avoiding such fluctuations of the spring prestress in dynamic systems, in a further embodiment, the diaphragm spring has in the relatively negative course of the characteristic curve, a spring force which is essentially constant along the operating range.
The present invention has a preferred application in the arrangement in DE-C 41 10 088, in which the diaphragm spring, while being supported against a shaft-side flange or against a ring non-rotatably connected with the flange, is arranged to be indirectly or directly affecting one of the faces of the driving wheel arranged to be movable with respect to the angle of rotation between the flange and the ring.
By fixing the operating range of the prestressed diaphragm spring in a relatively negative course of the characteristic curves selected in the end range of the maximal spring path, a device for friction damping is achieved which has an advantageously narrow construction in the axial direction.
For avoiding wear which may be caused by movements of the driving wheel with respect to the angle of rotation, the diaphragm spring advantageously affects one of the faces of the driving wheel by way of an intermediate ring. In order to also prevent wear between the diaphragm spring and an intermediate ring, the latter are arranged in a rotationally secured manner by supporting bolts which non-rotably connect the ring with the flange. For this purpose, the diaphragm spring have recesses which are configured to be adapted to the supporting bolts; particularly recesses are provided on the outer edge of the diaphragm spring, to be used as safety devices with respect to rotation.
In a further embodiment of the recesses of the diaphragm spring as slots which are penetrated by the supporting bolts, are radially directed and are preferably open on the side of the outer edge, the diaphragm spring can be selected corresponding to the given installation space in the radial dimension in the optimum manner with respect to the dimensions for the inside and outside diameters which also determine the spring characteristic.